This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Recently, a novel imaging method for imaging lung perfusion and pulmonary gas exchange has been developed at CIVM. It is based on venous injection (tail vein or jugular vein) of hyperpolarized (HP) 129Xe dissolved in saline. 129Xe is cleared through the lungs where it can be imaged with relatively high resolution. In addition to mapping perfusion, quantitative information may be obtained from repetitive imaging or spectroscopy and adaptation of the Kety-Schmidt theory. The new project aims at avoiding injection of larger quantities of fluid by replacing injections of HP 129Xe dissolved in saline with direct gas injections. To avoid creation of pulmonary embolism due to production of gas bubbles during the injections, a novel type of catheter will be used. The catheter contains a microporous hollow-fiber membrane (a thin-walled, opaque, polymer membrane that is used in a variety of medical, controlled-release, or biotechnological applications). It features submicron porosity, relatively high burst strengths, and excellent chemical resistance. Due to their hydrophobic properties and small pore size, the membrane resists water permeation, except at high pressures. The project will be divided into three phases: (1) verification of the bubble-free 129Xe injection into aqueous fluids in a phantom experiment;(2) replication of previous results obtained with saline injections by using membrane-facilitated direct gas injections in 10 rats;(3) high-resolution perfusion imaging (in-plane submillimeter voxel dimensions, slice thickness 5mm or less) in 10 rats.